1. Field of Invention
The present invention relates generally to the field of providing content over a network and other distribution channels, and specifically in one embodiment to bandwidth recovery in a switched network environment.
2. Description of Related Technology
One significant competitive challenge presently faced by network operators relates to managing and conserving bandwidth. This includes the reclamation of otherwise under-utilized or unused bandwidth such that the service and/or customer base can be expanded without significant modifications or build-outs of the underlying network infrastructure. For example, it is clearly desirable to expand the types and availability of “next-generation” network services, including high-definition (HD) broadcast, VOD, high-speed data, VoIP, Interactive TV, etc. over time, without the need for major capital expenditures or system modifications. Hence, network operators are increasingly focused on techniques for “squeezing” as much capacity out of their existing networks as possible.
The foregoing need for bandwidth optimization and reclamation is also applicable to so-called “switched” network architectures. These architectures generally distribute all of the available content provided by the network operator (e.g., multiple systems operator, or MSO) to switches within the network; these switches are then used to selectively provide only those channels actually watched or requested by users to their hubs or nodes for delivery, thereby effectively deleting unwatched channels from the digital broadcast stream. A “deleted” channel is automatically switched back on when a subscriber subsequently selects it, with the switching and delivery transition being for all intents and purposes transparent to the subscriber. This approach has obvious benefits from the standpoint of bandwidth conservation.
Bandwidth Recovery
A BSA system must at least periodically recover bandwidth to operate. If bandwidth is not recovered, the QAM pool will become clogged with stale streams—streams with tuners but no viewers. Viewership qualification and bandwidth recovery are salient factors differentiating BSA systems form simple multicast systems. Viewership must be qualified in a well-considered and “respectful” way in order to derive the greatest benefit to all viewers.
An ideal BSA system should be efficient and robust in the face of over-subscription pressure. However, betterment of these goals should also be considered in the context of a transparent user experience. Ideally, the subscriber is not aware of any difference between BSA program viewing and broadcast program viewing.
A ready amount of bandwidth workspace within the BSA system makes possible rapid stream setup for fast response to program viewing requests. The most desirable and frequent means to build and maintain this workspace is through tuner tracking. The bandwidth workspace grows when viewers vacate the BSA pool, such as by tuning away or turning off their CPE (e.g., settops).
When this technique alone is not sufficient, bandwidth recovery processes are used. In the great majority of cases, operation of these processes will not be known to the subscriber, thereby maintaining the desired transparency.
Within the BSA system, some program streams are allowed to continue to flow even when all known tuners have tuned away. These streams may be being viewed by non-responding clients that do not have upstream connections. This technique makes the system more robust, in that loss of two-way connectivity appears to the customer as a partial loss of programming, and not a complete outage.
The prior art discloses a variety of techniques relating to the reclamation of bandwidth in a content-based network. For example, U.S. Pat. No. 5,838,921 to Speeter issued Nov. 17, 1998 and entitled “Distributed connection management system with replication” discloses a distributed connection management system for an interactive multimedia network that controls the allocation and recovery of bandwidth resources in the network between client and server. The connection manager accepts as input the topology of a network to be controlled and partitions the local access portion of the network into separately administered neighborhoods. Resources for each of the partitioned neighborhoods are allocated by a replicated neighborhood connection manager. The remainder of the network is partitioned into the switched ATM network and into server network resources. Resources within the switched ATM network are administered by an ATM connection manager. Resources into and out of the servers are managed using a server connection manager. A connection within the network is achieved through the neighborhood connection manager by determining the other components of the connection manager needed to achieve the connection and combining the resources allocated by all three components of the connection manager and returning them to the client.
U.S. Pat. No. 6,909,726 to Sheeran issued Jun. 21, 2005 and entitled “Adaptive bandwidth system and method for broadcast data” discloses a system and method for optimizing bandwidth efficiencies in the distribution of digital video, digital audio and data over a cable television system. Different transmission channels or portions thereof can be dynamically customized to contain only those digital video, digital audio and data components of value at that time to the customers served by those channels. This customization requires a dynamic bandwidth management component which has the ability to monitor and react to changing customer usage patterns and to instruct a re-multiplexor to allocate bandwidth from digital services that require less bandwidth at a given time to services that require more bandwidth.
Various techniques for resource management are also evidenced in the prior art. See, e.g., U.S. Pat. No. 6,643,262 to Larsson, et al. issued Nov. 4, 2003 and entitled “System and method for dynamic sharing of connection resources” which discloses a system and method for the efficient utilization of core telecommunications resources (including both switching and transport resources) during a datacom session over a connection-oriented telecommunications system is described. First, the telecommunications resources along a connection path are partitioned into two or more segments. One or more pause sensors placed along the connection path detect periods of inactivity in a connection. Whenever such a period of inactivity is detected, the pause sensor selectively causes the release of core telecommunications resources for reallocation to active applications, typically by deactivating one or more segments. When wake-up sensors detect renewed activity over the connection, then the dormant connection is reactivated by reallocating core physical resources. The dynamic connection technique can be used both with analog (inband) signaling systems (e.g., Plain Old Telephone Service) as well as with digital signaling systems (e.g., Integrated Services Digital Network). The deactivation and reactivation of core telecommunications resources can be performed using various priority schemes.
Still other prior art teaches methods of rationing or allocating the amount of bandwidth utilized. For example, U.S. Pat. No. 5,822,530 to Brown issued Oct. 13, 1998 and entitled “Method and apparatus for processing requests for video on demand versions of interactive applications” discloses an interactive communication system, a method and apparatus for processing requests for video-on-demand versions of interactive applications. One embodiment initially receives a request to transmit a video on-demand version of a particular interactive application. This embodiment then determines if transmission of this video-on-demand version would constrain resources of the interactive communication system. If the system's resources would not be constrained, the interactive system provides the viewer with the video-on-demand version of the interactive application. On the other hand, if the system's resources would be constrained by the transmission of the VOD version, then the invention (1) denies the request for the video-on-demand version, and (2) directs the requesting viewer to view a near video-on-demand version of the particular application.
U.S. Pat. No. 6,473,793 to Dillon, et al. issued Oct. 29, 2002 and entitled “Method and apparatus for selectively allocating and enforcing bandwidth usage requirements on network users” discloses a hybrid gateway which includes functionality that allows bandwidth on a network (such as a satellite link) to be dynamically allocated and enforced. The hybrid gateway compares the thresholds defined for a requesting terminal's level of service and its measured running average data throughput to determine if the requesting terminal's bandwidth should be reduced (throttled). The hybrid gateway intercepts requests made by the requesting terminals and, if necessary, reduces the advertized window size of requests made by the requesting terminal, thereby reducing the transmission speed of the link and therefore the bandwidth of the link.
U.S. Pat. No. 5,940,738 to Rao issued Aug. 17, 1999 and entitled “Video pedestal network” discloses an architecture for distributing digital information to subscriber units wherein selection from among multiple digital services is accomplished by transmitting a tuning command from a subscriber unit to an intermediate interface. The intermediate interface selects the desired service from a broadband network and transmits it to the subscriber unit over a bandwidth-constrained access line. The bandwidth-constrained access line may be implemented with existing infrastructure, yet the subscriber unit may access a wide variety of digital information available on the broadband network. Universal broadband access is thus provided at low cost. Output bandwidth of broadcast equipment may also be optimized.
U.S. Pat. No. 6,718,552 to Goode issued Apr. 6, 2004 and entitled “Network bandwidth optimization by dynamic channel allocation” discloses an information delivery system which provides programming, such as video programming, by dynamically allocating the programming to channel slots, based on the availability of the channel slots. Programming with high viewership statistics is transmitted substantially continuously and programming with lower viewership statistics is transmitted “on-demand” in response to requests by users by way of a subscriber station. The subscriber stations maintain a map, provided by a corresponding session control manager, of currently available and currently transmitted channels. The information delivery system, in a preferred embodiment, takes the form of a Hybrid Fiber Coaxial system.
U.S. Pat. No. 7,207,055 to Hendricks et al. issued Apr. 17, 2007 and entitled “Bandwidth allocation for a television program delivery system” discloses a method for selecting specific programs from a plurality of programs, allocating the selected programs to a segment of bandwidth, and continuing to allocate the programs until all the programs are allocated or all of the available bandwidth is allocated. The programs may be selected based on a variety of different factors or combination of factors. The selected programs may also be prioritized so that higher priority programs are distributed before lower priority programs in case there is not enough bandwidth to transmit all of the programs. This invention allows a television program delivery system to prioritize a large number of television programs and distribute these programs based on their priority levels. The invention also permits a television program delivery system to dynamically allocate bandwidth over time or based on marketing information, such as consumer demand.
Still, other prior art discloses a variety of methods of reducing the amount of bandwidth that is needed to transmit content. For example, U.S. Pat. No. 7,336,787 to Unger et al. issued Feb. 26, 2008 and entitled “Critical packet partial encryption” discloses an encryption arrangement for multiple encryption of television programs. A system according to embodiments of the invention multiple-encrypts only a portion of the data required for full presentation of a television program to permit coexistence of multiple conditional access encryption systems associated with multiple manufacturer's set-top boxes within a single system. In one embodiment, only critical packets such as those carrying a payload incorporating packetized elementary stream header information is encrypted. By only encrypting a portion of the program, dramatically less bandwidth is consumed than the alternative of multiple encryption of all program data, thus permitting a larger number of programs to be carried over the same bandwidth while permitting coexistence of multiple conditional access systems in a single cable television system.
In spite of the foregoing approaches on how to manage bandwidth use and maximize bandwidth efficiency, there remains a salient need for a method and apparatus to address those situations where insufficient bandwidth exists to service all of the requests. There are no signs that the demand for bandwidth in content-based networks will subside over time due to, inter alia, increased penetration of high-definition services, etc. It is inevitable that, without increasing the infrastructure of the BSA network, there will come a time when extant bandwidth recovery methods will be an incomplete solution to the foregoing needs.
Previous solutions employed a rather simplistic and “coarse” technique; i.e., select a group of viewers that will have their service denied (based on Quality of Service agreements or the like) when there is insufficient bandwidth. But this solution is too “blunt”; some viewers would be denied their programs unnecessarily because it was unnecessary to recover their bandwidth. Or, conversely, a viewer would be denied their program because not enough bandwidth was recovered.
Hence, a more precise methods and apparatus for recovering bandwidth, especially in switched networks, is needed. Such improved methods and apparatus would ensure that enough bandwidth was recovered to satisfy viewer requests or alternatively, if enough bandwidth was not available and some viewers requests were denied, the number of viewers that were denied service would be minimized.